Introduce `normalizeToMp3` utility to convert wav/ogg audio buffers from TTS providers
to mp3, ensuring consistent mp3-only handling in cache and pipelines. Add logic to
detect and adapt to OpenAI-compatible servers that do not support explicit
`response_format`, falling back to default output and normalizing as needed.
Refactor voice resolution to probe multiple common endpoints and robustly extract
voice/style names from various payload shapes, improving compatibility with custom
OpenAI-compatible servers.
- Add `audio-format.ts` for audio normalization utilities
- Add tests for audio format normalization
- Update TTS provider request logic to apply normalization and handle response format negotiation
- Enhance voice endpoint probing and extraction logic for custom servers
